Weed Killer Worker now has summary lines available through a new command-line switch “/c” (counts).  After each server, and each configuration entry, it will display the number of files removed and the number of bytes recovered from the file deletions.

Note: The byte size is a minumum recovered size.  It does not actually factor in bytes recovered from unused, allocated space in clusters, so the actual recovered size is almost always slightly higher.

See the download section for details.

It seems appropriate to talk about this class, with the switch from Daylight Savings Time to Standard Time occurring this coming weekend in the United States. I’ve done a bit of work with this class lately, and wanted to share a test application I wrote to demonstrate some conversions. It also shows the effects which occur during the actual time change, when converting between time zones. You will need the .NET Framework 3.5 installed to use this demo.

The console application shown here shows how to iterate the defined Time Zones, convert from UTC to the Eastern Time Zone, and Convert from Eastern Time to Pacific Time using UTC as a midpoint in the conversion.  All this is done with the TimeZoneInfo class.  Eastern and Pacific time zones (US) are arbitrary choices: any time zone can be used.

I designed the example times used in the demonstration to show the variances which occur between two times zones, during the actual day of a time change. It also shows the local time ambiguity which occurs during the two occurrences of 2AM in the fall, and the absence of 2AM in the spring.

While the demonstration provides practical examples of how to do these conversions, I hope you will see the value of storing time as UTC instead of its local value in critical applications.  Any time a change occurs, there is a one hour period per year where an occurrence in the 2AM hour will be ambiguous when the date is localized: did it occur before the change or after the change.  If the date recorded is UTC, the ambiguity does not exist.

While most applications can live with one hour of ambiguity in the time per year, especially since it’s a time when most people are asleep, it is an important design consideration in critical applications.

While enhancing the Weed Killer application, I ran into an interesting problem trying to make Weed Killer a single instance application.  There are several ways to do this: one is to use the semi-dreaded mutex. Surprisingly, the easiest way turned out to be implementing a class in the Microsoft.VisualBasic namespace from the .NET 2.0 framework: WindowsFormsApplicationBase.

But, at first, it may not seem like the easiest way.  I had to make several attempts to get my inheriting class right.  I ran into a lot of examples on the net which were not great fits for what I was trying to do.  And some of the examples were right in principal, but the code didn’t work.

The class shown here can be used for your own code, by just replacing the form you instantiate in the startup event.  ManagerMDI is the entry point for the application.  Its method OpenFile() takes a single parameter: the file to open.  It internally manages whether the file is already open in a child window, or if a new window needs to be open.

The value of inheriting from the WindowsFormsApplicationBase base class is obvious: all of the housekeeping for determining whether an instance is running or not is taken care of for the developer.  The two startup cases are handled easily using specific events: Startup if you’re the first, or StartupNextInstance if you’re not the first.

One little note:  The method SetForegroundWindow() from user32.dll is used to set focus on the application, at the end of the StartupNextInstance event.  I also use it in the Startup event, in case the application was launched from an outside source (e.g. Windows Explorer context) though it probably isn’t needed there.  The behavior of this method is dependent on a setting for limiting focus, which you can see in Powertoys for WinXP, etc (General / Focus).  If “prevent applications from stealing focus” is enabled, the method will cause the application’s taskbar entry to flash.  When disabled, the application will be restored and receive focus on the desktop.

This has some small changes to the configuration (Regular Expression versus Wildcards is now an enumeration), and the Manager is now a single-instance application.

Source code and binaries are available on the SourceForge.net project page.

Wow !  The mysterious and annoying RDC problem on my laptop took a dangerous turn yesterday.  The problem has to do with the power setting properties sometimes mutating, when I bring my Windows XP Media Center laptop out of hibernation, and connect to it via RDC.  The original problem is described in this post.

Apple released the new 3.1 O/S for the iPhone.  Having a very busy week, I decided to start downloading the software and the firmware installation after I was setup at work.  I was not going to stay up for the buzz of the new Apple release.  So I setup everything in the morning, and I was able to launch the whole process via RDC on the laptop, switch back to my “work”-station, and be productive while the upgrade process ran automagically.

After 15-minutes, I got up to take a break and, while on it, had this sudden feeling of dread come over me.  I had not verified that the standby and hibernation timeouts were still set to “never” after I connected via RDC.  So I hurried back to my desk and checked.

Sure enough, the settings had mutated to 20 minute standby, and 30 minute hibernation for external power.  D*!@mn 1t  !!  As I discovered this, the iPhone was displaying the Apple logo, with a progress bar under it just starting to fill.  I obviously came back in time.  Had the laptop gone into standby and hibernation, it would have screwed the firmware load, and I would have been on the phone with Apple support (at a minimum) to get this fixed.

I still have seen no information on this problem with mutating standby and hibernation settings, and I got a very ugly taste of what damage it can potentially do.  Microsoft… find this and fix this !!!

BREAK and CONTINUE are two forms of loop control, which I have seen under-used lately.  I think it is time to revisit how these two statements can help you make more maintainable and readable code, with some basic comments where needed.

BREAK is used to prematurely exit a loop sequence, be it a WHILE loop, or a FOR loop.  CONTINUE is used to force the next iteration of the loop.  These two keywords exist verbatim in SQL and C/C#/Java, but all languages have them in some dialect.

A great way to understand easier maintenance is the venerable CURSOR in SQL.  Generally, a cursor loop is written as such:

SQL Cursor Loop, Common Technique

This code is very familiar to SQL developers. The @@FETCH_STATUS value becomes non-zero if no further records are available, or some other error occurs.  The problem with this code is that if a column in the select statement is added, dropped or changed, there are three points of maintenance: the declare statement, and two fetch statements.  If the loop is rather large, the last fetch statement is going to be a long way down.

Consider the following change to the code:
SQL Cursor Loop, Refactored

The change makes the WHILE loop appear infinite, but it simply guarantees that the execution will always enter the loop.  Notice that I explicitly put a comment there to ensure that anyone maintaining the code understands the intent.  Since the FETCH statement is identical for the first and successive records, that is what will occur with the same statement–on the initial entry and upon successive iterations.  The IF statement checks for either no more records or an error condition, and will trigger the BREAK statement when that happens.  Otherwise, the code below the IF statement continues to execute, and will iterate back to the WHILE statement.  This scenario also covers the case of no rows returned by the SELECT statement.  The BREAK statement immediately exists the WHILE loop, executing the CLOSE statement.

This now reduces maintenance to a DECLARE statement and a single FETCH statement.  To me, the code is also more readable.  My first instinct reading the original code is to question why the FETCH statement was repeated in the original code (it’s just because of the way my brain works).

BREAK and CONTINUE are extremely useful for creating short-circuiting logic, within a main logic condition.  Example: Say you needed to parse a set of command arguments, where certain argument combinations would cause remaining arguments to be ignored, or cause the single argument to be ignored.  The code could be written like this.

As Labor Day came and went, I began thinking about all that’s been happening in American politics, and some of the quandaries we have as a country.   Our Labor Day holiday is based on celebrating the American workers and their accomplishments, by… well, I guess by giving them a break from their work.

Labor Day has always been a strange day for me, especially after living in Europe for over five years.  The US holiday has been in existence since 1882, and has its origin during the industrial era of the Western World.  It is very similar to the May Day holiday, which the Communist and Socialist World embraces.  The biggest difference between the two holidays to me is that in America, we celebrate the time-off with our families and friends, having picnics and recreational getaways.  May Day celebrations around the world seem to manifest as some galvanizing protest, with large amounts of energy spent on chanting and in many cases vandalism.

How we celebrate Labor Day versus other countries celebrating May Day is only one aspect.  I could go on for hours about self-image, and about how a person identifies their self-worth with their work manifests in these celebrations.

But I have an important question.  When are we, as a country, going to offically recognize our own economic system and create a holiday called Free Enterprise Day ?

Why is it in the United States, the world’s dominant superpower and sanctuary of capitalism, we have no official holiday celebrating business owners.  That’s right.. ownership.  I always chuckle when I hear about Government efforts to create “jobs.”  It’s a buzz word that politicians use because they know that most people can relate to the steady paycheck, and work for someone else’s business. But in reality, jobs are created by passing a number of tax laws or grant programs to give enough incentive to people thinking about starting a business–so that they actually can do it.  And it is those people who cross over the line, and many times burn bridges doing so, that end up creating those jobs that the politicians are so desperately promoting.

Did anyone ever take note that in the late 1970’s, before Soviet-style Communism was on the decline in the 1980’s, China began a shift to market-based economics and partial private ownership under Deng Xiaoping’s leadership.  He sowed the seeds which make China’s economic presence so powerful today.  When the Soviet bloc was crumbling, China was growing and beginning to prosper, and has moved into the position of the next Super Power.  Granted, China does not have the extreme free-market style that the US has, but as you can see, a little Capitalism goes a long way.

So, as the next Labor Day holiday approaches, think about what you are celebrating.  In this economy, it’s great to celebrate having a job.  Just keep your thinking a little broader.  Take the time to remember and thank those who dared to step over the line and create the business you work for.

After all, that’s what keeps the Labor force, blue or white collar, employed.  And if you take the time to learn the demands of leadership and perseverance that business owners endure to make their vision survive and prosper, I think you will understand that a nationally recognized day for business ownership is long overdue.

Ted Kennedy’s passing marks a great loss to America.  And, unfortunately, now it’s time to watch the politics of America overtly abuse his death as a reason that a bad bill should be passed.  All because the Senator’s long-term goal was health care reform.

And, of course, the media now furiously broadcasts the personal involvement Senator Kennedy had with health care reform.  While they didn’t said it in their broadcasts, there was an ugly, unspoken undertone in the messages: wouldn’t it be an insult to Senator Ted Kennedy’s life work if the health care reform, which he fought so hard for, would fail to pass.

Argumentum ad Misericordiam  (Argument based on Pity) ..

This is one of the classic argument traps, and the one you will see used in the media and by the Obama administration over the next several days and weeks. I found this great example of it here, reprinted below.

An Appeal to Pity is a fallacy in which a person substitutes a claim intended to create pity for evidence in an argument. The form of the “argument” is as follows

• P is presented, with the intent to create pity.
• C is true.

This line of “reasoning” is fallacious because pity does not serve as evidence for a claim. This is extremely clear in the following case: “You must accept that 1+1=46, after all I’m dying…” While you may pity me because I am dying, it would hardly make my claim true.

So up the aspirin dosage as need be while tolerating the media circus.  But keep in mind that the final desperate weeks are here for Obamacare.  And it shouldn’t be any surprise that politicians will abuse Senator Kennedy’s memory to try and sway the tide of opposition.

But nothing has changed: a bad bill is still bad bill.

This has a small bug correction for Weeks as an age metric, and the help file is now launched into the default browser.  This appears to be the final Alpha release.

All source code and binaries are now on the SourceForge.net project page.  Please visit that site for further details as the project develops.

I’ve been maintaining the project using Visual Studio 2008 and the AnkhSVN plugin for Visual Studio, with the source repository set directly to the AVN server at SourceForge.net.

Weed Killer Manager now has small fixes to the behavior of selected events in the Tester (and their coloring).  I’ve also added a count and size display to the group box header for event selection.  It shows the counts and total bytes for all items in the selected events.  It allows for estimating or measuring impact on disk space and file count.

Weed Killer is now available on SourceForge, which has the updated binaries. You may also download them from the project page here.